21128415840 has 720 divisors, whose sum is σ = 87889408992. Its totient is φ = 4779565056.

The previous prime is 21128415839. The next prime is 21128415851. The reversal of 21128415840 is 4851482112.

21128415840 is a `hidden beast` number, since 2 + 11 + 28 + 41 + 584 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21128415795 and 21128415804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 217818672 + ... + 217818768.

Almost surely, 2^21128415840 is an apocalyptic number.

21128415840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21128415840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43944704496).

21128415840 is an abundant number, since it is smaller than the sum of its proper divisors (66760993152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21128415840 is an frugal number, since it uses more digits than its factorization.

21128415840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 20480, while the sum is 36.

Adding to 21128415840 its reverse (4851482112), we get a palindrome (25979897952).

The spelling of 21128415840 in words is "twenty-one billion, one hundred twenty-eight million, four hundred fifteen thousand, eight hundred forty".